Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 176	$ 237	$ 312
Liabilities, Fair Value Disclosure, Recurring	1,252	1,727	1,733
Other Current Assets | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	21	58	78
Other Current Assets | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		5	20
Other Current Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		1	2
Other Current Assets | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1
Other Noncurrent Assets | Common stock shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	4	4	5
Other Noncurrent Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	3	5	2
Other Noncurrent Assets | Equity swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	147	164	205
Other Current Liabilities | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	60	63	72
Other Current Liabilities | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	7	1
Other Current Liabilities | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	3	7	7
Current Portion of Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	403	801	801
Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	450	855	853
Long-Term Debt | Foreign Currency Denominated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	329
Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	151	168	210
Liabilities, Fair Value Disclosure, Recurring	329	0	0
Quoted Prices in Active Markets (Level 1) | Other Current Assets | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Quoted Prices in Active Markets (Level 1) | Other Current Assets | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		0	0
Quoted Prices in Active Markets (Level 1) | Other Current Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		0	0
Quoted Prices in Active Markets (Level 1) | Other Current Assets | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Quoted Prices in Active Markets (Level 1) | Other Noncurrent Assets | Common stock shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	4	4	5
Quoted Prices in Active Markets (Level 1) | Other Noncurrent Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Quoted Prices in Active Markets (Level 1) | Other Noncurrent Assets | Equity swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	147	164	205
Quoted Prices in Active Markets (Level 1) | Other Current Liabilities | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Quoted Prices in Active Markets (Level 1) | Other Current Liabilities | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0
Quoted Prices in Active Markets (Level 1) | Other Current Liabilities | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Quoted Prices in Active Markets (Level 1) | Current Portion of Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Quoted Prices in Active Markets (Level 1) | Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Quoted Prices in Active Markets (Level 1) | Long-Term Debt | Foreign Currency Denominated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	329
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	25	69	102
Liabilities, Fair Value Disclosure, Recurring	923	1,727	1,733
Significant Other Observable Inputs (Level 2) | Other Current Assets | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	21	58	78
Significant Other Observable Inputs (Level 2) | Other Current Assets | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		5	20
Significant Other Observable Inputs (Level 2) | Other Current Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		1	2
Significant Other Observable Inputs (Level 2) | Other Current Assets | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1
Significant Other Observable Inputs (Level 2) | Other Noncurrent Assets | Common stock shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Significant Other Observable Inputs (Level 2) | Other Noncurrent Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	3	5	2
Significant Other Observable Inputs (Level 2) | Other Noncurrent Assets | Equity swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Significant Other Observable Inputs (Level 2) | Other Current Liabilities | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	60	63	72
Significant Other Observable Inputs (Level 2) | Other Current Liabilities | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	7	1
Significant Other Observable Inputs (Level 2) | Other Current Liabilities | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	3	7	7
Significant Other Observable Inputs (Level 2) | Current Portion of Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	403	801	801
Significant Other Observable Inputs (Level 2) | Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	450	855	853
Significant Other Observable Inputs (Level 2) | Long-Term Debt | Foreign Currency Denominated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Other Current Assets | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Other Current Assets | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		0	0
Significant Unobservable Inputs (Level 3) | Other Current Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		0	0
Significant Unobservable Inputs (Level 3) | Other Current Assets | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Significant Unobservable Inputs (Level 3) | Other Noncurrent Assets | Common stock shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Other Noncurrent Assets | Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Other Noncurrent Assets | Equity swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Other Current Liabilities | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Other Current Liabilities | Cross-Currency Interest Rate Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0
Significant Unobservable Inputs (Level 3) | Other Current Liabilities | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Current Portion of Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	0	0
Significant Unobservable Inputs (Level 3) | Long-Term Debt | Fixed Rate Debt Swapped to Floating
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	0	$ 0	$ 0
Significant Unobservable Inputs (Level 3) | Long-Term Debt | Foreign Currency Denominated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	$ 0